This invention relates a grinder and a method of manufacturing the same, and more particularly a grinder having a definite grinding particle distribution pattern on the surface of the grinder.
Since the development of a grinder made of cubic crystalline boron nitride (CBN), the request for improving the capability of the grinder has become increasing, especially;
(I) to eliminate as far as possible the random elements in the grinder for enabling quantitative determination and change the grinder performance and
(II) to eliminate as far as possible not effective cutting edges, thereby producing inexpensive grinders of high performance.
As disclosed in Japanese Patent Application No. 15445 of 1985, the following method has been proposed for eliminating a random distribution of the grinding cutting edges which is considered as the greatest cause of the random performance of the grinder, thereby providing a grinder having a grinding particle distribution satisfying a definite rules.
According to this method, a pattern that determines the fixed position of the grinding particles is formed by an electroconductive layer on the surface of a sheet having a predetermined configuration, then the resin sheet formed with the pattern of the electroconductive layer is dipped in an electrolytic bath containing metal ions and incorporated with grinding particles, and the grinding particles are fixed on the pattern of the electroconductive layer by passing electric current between the electroconductive layer and a counter electrode. Then the resulting resin sheets secured with the grinding particles are laminated with a filler resin powder or a filler resin sheet interposed between the resin sheets and the laminated resin sheets are molded under pressure of an elevated temperature.
This method provides a grinder in which the grinding particles are distributed in a predetermined pattern on the surface of the grinder having higher grinding performance than the prior art grinder. In this grinder, however, the density of the grinding particle distribution, the condition of supplying a grinding liquid and the vibration produced at the time of grinding which are the principal causes that have an influence upon the grinding performance, are not controlled, thus failing to provide an excellent grinding performance. According to this method, although it is possible to ensure a grinding particle distribution according to a definite rule, since the pattern for securely fixing the grinding particles is formed by an electroconductive layer, it is necessary to use an expensive electroconductive ink for printing the pattern. Furthermore, it is necessary to print an insulator for preventing the grinding particles from adhering to the electroconductive layer for the purpose of improving the performance of the grinder. Thus this method requires two steps. Therefore, it is not only expensive but also difficult to prepare the pattern.
Moreover, since a long time is required for growing a plated film on the pattern, it takes a long time for securing the grinding particles to the pattern, thus prolonging the time for manufacturing the grinder. Moreover, as it is necessary to dip the resin sheet in a metal ion containing electrolytic bath, the components of the resin sheets are dissolved in the bath, thus degrading the same.
Since the grinding particles are secured to the pattern made up of an electroconductive layer by passing electric current, the grinding particles are limited to a non-electroconductive material. For this reason, where the nickel coated grinding particles are used, it is necessary to use the particles after recoating.
Where the line width of the pattern is narrow, it becomes easy to control the grain particle distribution. With this measure, however, the patterns becomes discontinuous, thus disenabling fixing of the grinding particles so that it is impossible to make extremely narrow the line width of the pattern. Thus, there is a limit for the control of the grinding particle distribution.